Pwm RPM control

[b57378]

Hi all, hope you are all doing well.

Just a quick question.

I am using a generic 5-axis breakout board with Uc400 controller and I am controlling the spindle speed via the PMW 0-10v signal.

A problem I am having is the max voltage output is about 9.8VDC which only gives me 21000RPM. If I command S12000 it should be around 5V but outputs about 3.9V.

The supply to the BOB reads out exactly 24VDC so no problem with low supply.

My min and max RPM is set as 5000 and 24000 respectively.

Any ideas? Thank you in advance.

[ger21]

Most PWM to analog speed control circuits will have a ~0.2 voltage drop at max RPM.
But a good one should be giving you 5V at 12,000 RPM.

So my first suggestion would be to get a better speed control.

What I did to get around the 9.8V problem, was to set the PWM max to 50%, and set the VFD to accept 0-5V instead of 0-10V. This worked perfectly.

[b57378]

Great, thank you for the help! - that makes sense, I'll do that.

[b57378]

I suppose with 0-5V you will lose some precision of range but the RPM will be more proportional to the voltage.